Sahih Al Bukhari – Book of Oppressions

Volumn 003, Book 043, Hadith Number 645.
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Narated By Abu Said Al-Khudri RA : The Prophet PBUH said, "Beware! Avoid sitting on he roads (ways)." The people said, "There is no way out of it as these are our sitting places where we have talks." The Prophet said, "If you must sit there, then observe the rights of the way." They asked, "What are the rights of the way?" He said, "They are the lowering of your gazes (on seeing what is illegal to look at), refraining from harming people, returning greetings, advocating good and forbidding evil."